Dielectric responses and structure-property relationships of Ca_1-xBa_xWO₄ composite microwave dielectric ceramics

Ca_1-xBa_xWO₄ (x = 0–0.25, CBWO) composite microwave dielectric ceramics were obtained after sintering at 1200 °C for 4 h. X-ray diffraction and X-ray photoelectron spectroscopy were used to determine their complex phase structures. The lattice vibrational properties were revealed by Raman scattering and Fourier-transform infrared (FTIR) spectroscopy. The Raman spectra showed that phase-pure CaWO₄ had eight active vibrational modes when x = 0.15–0.25. A new vibrational mode appeared near 927 cm⁻¹, which was attributed to BaWO₄. The intrinsic properties were fitted and simulated by the four-parameter semi-quantum model according to the FTIR spectra. The low-frequency vibrational modes made a greater contribution to the intrinsic properties than the high-frequency modes. Structure-property relationships of the CBWO ceramics were obtained using Raman spectroscopy, and their dielectric responses were elucidated. The CBWO ceramic at x = 0.25 had excellent dielectric properties with ε_r = 7.43 and Q × f = 56,929 GHz.